That looks an awful lot like a honeydew melon, though it could be some sort of hybrid. It's hard to definitively identify without seeing the flesh, as the skin is basically identical to a honeydew.
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OmniaFaciatJul 29 '13 at 5:17

1

How does it look on the inside ... and what are the taste and texture like? It could be a very young squash/pumpkin of many varieties ... but it is hard to say from the picture.
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Martin TurjakJul 29 '13 at 9:13

3

Looks like some kind of heirloom zucchini.
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James McLeodJul 29 '13 at 10:50

Sorry guys, was trying to figure out what it was before I cut it up so I could plan out recipes. Heirloom zucchini seems to be it -- it did come side by side with another zucchini.
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Sherwin YuJul 29 '13 at 13:04

The fruit from the Cucurbit family (pumpkins, squash, zucchini, melons, gourds etc) are all very good at cross pollinating. This will create some very strange fruits.

I have accidentally grown all kinds of odd things. I would imagine that they are more common at markets & places where people sell produce grown on smaller (than commercial scale production) plots or gardens. This is because proximity is a contributing factor with wind & insect pollination.

I don't recognise this particular one but it could easily be hybrid. Was it the only one of its type or was there a whole crate of them?